idioms

问题 Within the C++ language, many will come across various design patterns that have a designated name in which we would call an Idiom, such as SFINAE , RAII , CRTP , Polymorphism , etc... Consider this following code snippet in its most basic form... template<typename T> auto make_object = [](T val) { class Foo { public: Foo(T val) : value_{val} {} T value() const { return value_; } private: T value_; }; Foo foo(val); return foo; }; // in some other code block, scope, or translation int main() {

问题 At first, our team found ourselves writing lots of code like this because that's what we're used to in languages like ActionScript. var arrayOfFoo : Array<Foo> = new Array<Foo>(); //Then, sometime later: var someFoo : Foo = arrayOfFoo[0]; someFoo.someFooMethod(); That's fine, but it can be simplified by relying more heavily on Typescript's type inference: //No need to declare the type ": Array<Foo>" here: var arrayOfFoo = new Array<Foo>(); //Again, no need to declare that someFoo is a Foo var

问题 I want to make a condition where all selected variables are not equal. My solution so far is to compare every pair which doesn't scale well: if A!=B and A!=C and B!=C: I want to do the same check for multiple variables, say five or more, and it gets quite confusing with that many. What can I do to make it simpler? 回答1: Create a set and check whether the number of elements in the set is the same as the number of variables in the list that you passed into it: >>> variables = [a, b, c, d, e] >>>

问题 So in Ruby there is a trick to specify infinity: 1.0/0 => Infinity I believe in Python you can do something like this float('inf') These are just examples though, I'm sure most languages have infinity in some capacity. When would you actually use this construct in the real world? Why would using it in a range be better than just using a boolean expression? For instance (0..1.0/0).include?(number) == (number >= 0) # True for all values of number => true To summarize, what I'm looking for is a

来源： https://stackoverflow.com/questions/8405453/is-there-a-shortcut-to-create-padded-array-in-javascript

来源： https://stackoverflow.com/questions/8405453/is-there-a-shortcut-to-create-padded-array-in-javascript

问题 To create all possible combinations of two sets of parameters and perform an action on them, you can do: setOf(foo, bar, baz).forEach { a -> setOf(0, 1).forEach { b -> /* use a and b */ } } However, if you have (potentially many) more parameters, this quickly turns into a pyramid of doom: setOf(foo, bar, baz).forEach { a -> setOf(0, 1).forEach { b -> setOf(true, false, null).forEach { c -> setOf("Hello,", "World!").forEach { d -> /* use a, b, c and d */ } } } } You could write this similarly

问题 In Linux header file epoll.h , I found the following code: enum EPOLL_EVENTS { EPOLLIN = 0x001, #define EPOLLIN EPOLLIN ... } What does it mean by #define EPOLLIN EPOLLIN ? 回答1: This create a macro named EPOLLIN whose replacement text is also EPOLLIN . This is most likely a way for the preprocessor to check which event codes are available and conditionally compile code as necessary. If we go to the git repo for glibc and look at the output of git blame we see the following for enum EPOLL

问题 In Linux header file epoll.h , I found the following code: enum EPOLL_EVENTS { EPOLLIN = 0x001, #define EPOLLIN EPOLLIN ... } What does it mean by #define EPOLLIN EPOLLIN ? 回答1: This create a macro named EPOLLIN whose replacement text is also EPOLLIN . This is most likely a way for the preprocessor to check which event codes are available and conditionally compile code as necessary. If we go to the git repo for glibc and look at the output of git blame we see the following for enum EPOLL

问题 This question already has answers here : Iterating C++ vector from the end to the begin (11 answers) Closed 5 hours ago . Suppose I'm a newbie C++ programmer. I have a C++ container; say, a vector: std::vector<int> vec { 12, 34, 56, 78 }; I know I can iterate over all of the elements with a simple loop: for(std::vector<int>::size_type i = 0; i < vec.size(); i++) { std::cout << vec[i] << '\n'; } and maybe I've even learned a little about Modern C++, so I know I can use a ranged-for loop: for